Paper/patches/server/0612-Entity-load-save-limit-per-chunk.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Jason Penilla <11360596+jpenilla@users.noreply.github.com>
Date: Wed, 18 Nov 2020 20:52:25 -0800
Subject: [PATCH] Entity load/save limit per chunk

Adds a config option to limit the number of entities saved and loaded
to a chunk. The default values of -1 disable the limit. Although
defaults are only included for certain entites, this allows setting
limits for any entity type.

diff --git a/src/main/java/net/minecraft/world/entity/EntityType.java b/src/main/java/net/minecraft/world/entity/EntityType.java
index e7bfd61be4974dbe6abc2ebb870664ff1fce19cb..ac0f0a4da4282c13f6e1f37710cb615d66b8ef2c 100644
--- a/src/main/java/net/minecraft/world/entity/EntityType.java
+++ b/src/main/java/net/minecraft/world/entity/EntityType.java
@@ -563,9 +563,20 @@ public class EntityType<T extends Entity> implements EntityTypeTest<Entity, T> {
         final Spliterator<? extends Tag> spliterator = entityNbtList.spliterator();
 
         return StreamSupport.stream(new Spliterator<Entity>() {
+            final java.util.Map<EntityType<?>, Integer> loadedEntityCounts = new java.util.HashMap<>(); // Paper
             public boolean tryAdvance(Consumer<? super Entity> consumer) {
                 return spliterator.tryAdvance((nbtbase) -> {
                     EntityType.loadEntityRecursive((CompoundTag) nbtbase, world, (entity) -> {
+                        // Paper start
+                        final EntityType<?> entityType = entity.getType();
+                        final int saveLimit = world.paperConfig().chunks.entityPerChunkSaveLimit.getOrDefault(entityType, -1);
+                        if (saveLimit > -1) {
+                            if (this.loadedEntityCounts.getOrDefault(entityType, 0) >= saveLimit) {
+                                return null;
+                            }
+                            this.loadedEntityCounts.merge(entityType, 1, Integer::sum);
+                        }
+                        // Paper end
                         consumer.accept(entity);
                         return entity;
                     });
diff --git a/src/main/java/net/minecraft/world/level/chunk/storage/EntityStorage.java b/src/main/java/net/minecraft/world/level/chunk/storage/EntityStorage.java
index dae66dd5dbebc7fd8fc331b1f5f06ec461667830..de7afc737b1ab099edc29a4ef94baa76329c2947 100644
--- a/src/main/java/net/minecraft/world/level/chunk/storage/EntityStorage.java
+++ b/src/main/java/net/minecraft/world/level/chunk/storage/EntityStorage.java
@@ -90,7 +90,18 @@ public class EntityStorage implements EntityPersistentStorage<Entity> {
 
         } else {
             ListTag listTag = new ListTag();
+            final java.util.Map<net.minecraft.world.entity.EntityType<?>, Integer> savedEntityCounts = new java.util.HashMap<>(); // Paper
             dataList.getEntities().forEach((entity) -> {
+                // Paper start
+                final EntityType<?> entityType = entity.getType();
+                final int saveLimit = this.level.paperConfig().chunks.entityPerChunkSaveLimit.getOrDefault(entityType, -1);
+                if (saveLimit > -1) {
+                    if (savedEntityCounts.getOrDefault(entityType, 0) >= saveLimit) {
+                        return;
+                    }
+                    savedEntityCounts.merge(entityType, 1, Integer::sum);
+                }
+                // Paper end
                 CompoundTag compoundTag = new CompoundTag();
                 if (entity.save(compoundTag)) {
                     listTag.add(compoundTag);